Piezoelectric element



June 13, 1950 A. DHALLOY I 2,511,624

PIEZOELECTRIC ELEMENT Filed March 30, 1946 Patented June 13, 1950PEEZOELECTRIC ELEMENT Audoin dHalloy, Paris, France; Hadidje NazliHamdi, widow and sole heir of said Audoin dHalioy, deceased ApplicationMarch 30, 1946, Serial No. 658,415, In France January 1944 Section 1,Public Law 690, August 8, 1946 Patent expires January 10, 1964 '7Claims. 1

My invention relates to piezo-elements and has as one of its objects theprovision of means for permanently protecting said element or elementsagainst the action of the medium inside which they are used and chieflyagainst the efiects of atmospheric moisture when the elements areexposed to the influence of climate and air; this protection of thepiezo-electric elements leads moreover to the possibility of using themin other media, such as water for instance, whereby their field ofapplication is widened.

My invention has also for its object the possibility of using forpiezo-electric elements, piezoelectric crystals which are to-day unfitto be used for certain applications; this is the case, for instance, iorcrystals which are deliquescent under the action of moisture.

I realize these objects by enclosing the piezoelectric element with adielectric substance selected so as to provide a perfect adherence ofthe enclosing substance with said piezo-electric element.

Preferably the improvement according to the invention may be executed byembedding the piezo-eiectric element within a dielectric substance suchas, for instance and chiefly, a metacrylic resin of the type known underthe registered trade name Plexiglas, the piezo-electric element beingintroduced inside the mass of plastic material before the polymerizationof the latter.

In order to allow my invention to be better understood I will describehereinafter by way of example and by no means in a limited sense,certain forms of execution thereof, the appended drawing illustratingsuch forms diagrammatically.

In said drawing:

Fig. 1 is a perspective view of a piezo-electric element made accordingto my invention.

Fig. 2 is a vertical cross-sectional view thereof.

Fig. 3 shows a vertical cross-sectional view of a modified form.

In said figures, i and I constitute quartz plates forming thepiezo-electric element associated with electrodes or armatures 5 formedin a manner known per se by thin metallic deposits or metallic elements;2, 3, and 3' are the leads or conductors adapted to connect the elementwith an amplifier; l designates a mass of dielectric substanceconstituted preferably by metacrylic resin of the type known as statedunder the registered trade name Plexiglas. The piezo-electric element isinserted inside a mould filled with the 2 corresponding monomericsubstance which is left to stand at a suitable temperature for producingits polymerization whereby finally said piezo-electrio element isembedded inside the mass 4 of dielectric substance together with theleads 2, 3 and 3'.

In the form of execution of Figs. 1 and 2, the piezo-electric element isentirely embedded within the mass 4, the thickness 4a of dielectricsubstance underneath the surface of the element adapted to be submittedto the compression or to stressing being very thin, and being in fact ifdesired totally or partially removed in front of the outer armature 5.

In the modification of Fig. 3, the upper surface of the piezo-electricelement is left bare.

Obviously, it is possible without widening the scope of my invention tomodify and improve various details in the execution of said invention.For instance, not only the leads 2, 3 and 3' but also part of theamplifier may be embedded inside the mass 4.

Having thus described the invention what is claimed as new and desiredto be secured by Letters Patent is:

1. A piezo-electric block comprising a piezoelectric element, and adielectric mass of metacrylic resin partly embedding therein saidelement.

2. The method for protecting a piezo-electric element against the actionof atmospheric eiiects consisting in embedding said element within adielectric resinous mass adapted to perfectly adhere to thepiezo-electric element.

3. The method for protecting a piezo-electric element against the actionof atmospheric and climatic media consisting in embedding said elementwithin a mass of metacrylic resin.

4. The method for embedding a Piezo-electric element at least partlywithin a protective mass consisting in placing said element within amass of monomeric material adapted to form through polymerization adielectric substance adhering to said piezo-electric element, andsubjecting said mass containing said piezo-electric element topolymerization.

5. A piezo-electric element structure comprising piezo-electric means,conductors, respectively, connected to said piezo-eiectric means, andplastic means adapted to adhere to and substantially completelyenclosing said piezo-electric means, said plastic means supporting saidconductors leading from said piezo-electric means to without saidplastic means and forming a dielectric mass.

6. A piezo-electric element structure comprising piezo-electric meansincluding metallic elements in contact therewith, conductor meansextending from said metallic elements, and a metacrylic substance atleast partly surrounding and encasing said piezo-electric means exceptfor one of said metallic elements and supporting said conductor means attheir connections and adjacent said piezo-electric means.

7. A piezo-electric element structure comprising piezo-electric meansincluding metallic elements in contact therewith, conductor meansextending from said metallic elements, and a metacrylic substancecompletely surrounding and encaslng said piezo-electric means andsupporting 4 said conductor means at their connections and adjacent saidpiezo-electric means.

AU'DOIN nHALLOY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,766,042 Nicolson June 24, 19301,812,977 Ohl July '7, 1931 2,386,692 Kuenstler Oct. 9, 1945 2,415,832Mason Feb. 18, 1947

